A liquid ejection apparatus includes a head having an ejection surface formed with opened ejection ports for ejecting liquid such as ink. If the liquid is not ejected from the ejection ports for a long time, water content of the liquid in the vicinity of the ejection ports is evaporated to increase viscosity, so that the ejection ports are clogged. There has been known a technique for suppressing such clogging of the ejection ports.
According to that technique, the ejection surface is covered by a capping part having a recessed shape, so that an ejection space isolated from an exterior space is formed. While humidified air is supplied from an air supply port to the ejection space by an air conditioning system including an air flow path having the air supply port and an air discharge port formed on a bottom surface of the capping part, the air in the ejection space is discharged from the air discharge port, so that the liquid in the vicinity of the ejection ports is humidified. Accordingly, the drying of the liquid in the vicinity of the ejection ports is suppressed, so that the clogging of the ejection ports is suppressed.
According to that technique, when the head is stored for a long time without being used, the viscosity of the liquid in the ejection ports may be increased even though the ejection space is humidified. Depending on degrees of the viscosity increase, the liquid is ejected from only the ejection ports in which the degree of the viscosity increase is low, even though the forcible suction purge operation is performed when using the apparatus again, and some ejection ports are left as being clogged. That is, the problem of the ejection defect is not solved in some ejection ports.